350 THE VOYAGE OF H.M.S. CHALLENGER. 
at about one-third of the distance from the centre to the margin. Its surface is covered 
with numerous and very fine strize, and the margin is raised, which gives the organ a 
“ put-on” appearance. 
The ambulacral tube-feet are very large, and have large fleshy sucker disks. 
Colour in alcohol, a bleached yellowish white. 
Locality.—Station 187. Booby Island, Torres Strait. September 9, 1874. Lat. 
10° 36’ 0” S., long. 141° 550” E. Depth 6 fathoms. Coral mud. Surface temperature 
77°'7 Fahr. 
Remarks.—This species shows affinities to Pentaceros westermanni and the group 
of forms allied to Pentaceros orientalis. Pentaceros callimorphus differs conspicuously 
from these, as well as from other members of the genus, by the character of the armature 
of the adambulacral plates (see foregoing description) ; and by the spinulation of the 
actinal intermediate plates,—the lineal arrangement of spinelets on the rows of inter- 
mediate plates external to the adambulacral plates on each side of the furrow imparting 
a very striking ornamentation to the actinal surface. The character and the uniformity 
of the size of the tubercles on the abactinal surface, as well as the large, regular, and 
well-defined papular areas, are also noteworthy. 
Genus Pentaceropsis, n. gen. 
All recent writers who have discussed the structural characters of Pentaceros 
obtusatus (Bory de Saint Vincent), Perrier, have thrown out the suggestion that its 
peculiarities demand generic recognition, but no one has been bold enough to actually 
place it apart. In taking this step now, I fear that I may incur the risk of drawing 
upon myself the stigma implied by the poet as merited by those whose footsteps are less 
timorous than those of more gifted persons! Having no desire to be accredited with wings 
at the expense of my convictions, I propose to call the genus Pentaceropsis, as indicating 
its affinity to Pentaceros. It is characterised by the generally flat form, by the presence 
of the intercalated series of plates between the supero-marginal and infero-marginal plates 
in the interbrachial arcs, and by the irregular character of the abactinal plating. 
Chorology of the Genus Pentaceropsis. 
a. Geographical distribution :-— 
Eastern ARCHIPELAGO and (?) INDIAN OcEAN: One species between the parallels 
of 20° N. and 30° 8. 
Pentaceropsis obtusatus, from the Philippine Islands, and also 
reputed to have been found at Mauritius. The latter locality appears 
to be doubtful. 
8. Bathymetrical range: Shallow water. 
y. Nature of the Sea-bottom: Not recorded. 
